A prominent Syrian journalist, Naji Jerf, known for his opposition to both President Bashar al-Assad and Islamic State has been shot dead in the Turkish town of Gaziantep.

Jerf was shot with a silenced handgun on Sunday afternoon, sources told Syrian news site Orient.

Jerf, originally from the western Syrian town of al-Salamiyah, was 38 and married with two children.

Jerf was a well-known figure among Syrian journalists and activists in Gaziantep and the rest of the diaspora.

His work training Syrian media activists and editing the magazine Hentah earned him the nickname “Uncle”.

Jerf suffered from health problems, and just days ago obtained a French visa to allow him to get medical treatment in safety.

One of Jerf’s last works was “Islamic State in Aleppo”, a documentary that exposed human rights violations committed by the group in the city.

A supporter of Islamic State wrote on social media on Sunday that the group had murdered the “heretic” Naji Jerf, although a police investigation to discover who was behind the killing is ongoing.

The killing comes just months after two anti-IS activists were beheaded in the Turkish town of Urfa.

Ibrahim Abdul Qader and Fares Hamidi were young activists who worked with the group Raqqa Is Being Silently Slaughtered to document human rights abuses committed by Islamic State in their Syrian hub of Raqqa.